Receptacle Termination & Wire Sizes

[thecrazyezel]

What is the largest size wire that can safely land on a receptacle termination? We normally use #12s everywhere, #10s for long distance runs but will #8s work? Is there some UL listed crimp than can be used or some other method that I do not know about that is legal and commonplace? Also, can you land #8s in a 30A disconnect switch or do you need to bump up to a 60A switch? As an engineer I lack the field experience with these issues and hope someone out there can help.

Thanks!
Joe

 

[haskindm]

110.14(A) limits the connection "by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent" for 10 AWG or smaller. Also look at the directions for the devices you are using to see what the manufacturer says. If you have runs long enough that you need to install #8 for a 15 or 20 amp receptacle, you should probably consider installing a sub-panel and then shorter branch circuits.

 

[infinity]

Another option would be to tail off each #8 with a #12 to install onto the device. Also disconnects will have the wire range for the lugs usually on the label on inside of the door. My guess is that most 30 amp disco's can take up to a #6 conductor.

 

[iwire]

If you have runs long enough that you need to install #8 for a 15 or 20 amp receptacle, you should probably consider installing a sub-panel and then shorter branch circuits.

I have to disagree here, we wire a lot of warehouse type buildings and you can not justify dropping a sub panel every couple of hundred feet. You would have panels with only about four circuits each.

I can tell you quite a bit of the wiring in your local Home Depot will be 6 and 8 AWG for 20 amp circuits.

Most of the chain stores we have worked with want all the panels in one or two locations, not distributed throughout.



Joe,

The largest I have had to run for 20 amp receptacle circuits has been 4 AWG CU. (per the engineer) for roof top outlets. At the receptacle location we would use a junction box and tap the 4 AWG with 10 AWG and run that to a device box.

At the panel end we installed a trough for splicing the 4 AWG to 10 AWG for the last 15' to the panel.

The short lengths of 10 AWG at each end of the up sized conductors make little difference in voltage drop over the total length.

Typical 15 and 20 amp devices will only accept 14 to 10 solid or stranded.

Breakers can be another issue. Some 15 and 20 amp breakers max out at 10 AWG while others may take a 6 AWG and if its a 600 volt breaker it might even take a 1 AWG.

 

[thecrazyezel]

Thanks to everyone who voiced their input. What I am gathering from this is that anything is possible. I agree with Bob about the subpanels...it is 3 or 4 of these circuits at 120/208V that are just far out and in different directions...I will be sure to pass all of this information along to our other engineers during our weekly discussion meetings. I think running #4s to the roof is a little crazy but you guys made it work. Interesting to know about home depot and the wiring.